THE WOODWARD ILLUMINATOR. 163 



illumination to die away. No w , again, good resol utions 

 can be obtained in the red similarly to those in the blue, 

 i. e., just at the point where the illumination begins to 

 decrease. It will now be quite time for those who have 

 never before used the instrument to look carefully to 

 the correction of the objective, and for the trial experi- 

 ment the object selected should be one that the observer 

 can master by the usual oblique illumination. It only 

 remains now to assure ourselves that the lamp is at the 

 proper distance from the stand, which is accomplished 

 by simply moving it farther away, or,_per co^ra, bring- 

 ing it nearer, sliding from right to left, and trying the 

 red and blue fields, as before instructed. The very best 

 position of the lamp as to distance is generally attested 

 by the general superior brilliancy of the illumination, 

 together with the fact that when this distance is just 

 right there will be room for greater lateral play of the 

 radiant without losing the illumination. Care should 

 be constantly observed to keep the lamp flame exactly 

 edgewise. It may be further stated that when things 

 are nearly in proper position, the smallest imaginable 

 movement of the lamp will often produce marked effects. 



THE WOODWARD ILLUMINATOR. 



For this novel and useful accessory microscopists are 

 indebted to Col. J. J. Woodward, of the U. S. Army. 

 A paper, giving a detailed account of the instrument, 

 by Col. Woodward, was read before the London Royal 

 Microscopical Society, and subsequently published in 

 the London Monthly Microscopical Journal. The paper 



